Global warming driven by rising greenhouse-gas concentrations is expected to cause wet regions of the tropics and mid to high latitudes to get wetter and subtropical dry regions to get drier and expand polewards1,2,3,4. Over southwest North America, models project a steady drop in precipitation minus evapotranspiration, P−E, the net flux of water at the land surface5,6,7, leading to, for example, a decline in Colorado River flow8,9,10,11. This would cause widespread and important social and ecological consequences12,13,14. Here, using new simulations from the Coupled Model Intercomparison Project Five, to be assessed in Intergovernmental Panel on Climate Change Assessment Report Five, we extend previous work by examining changes in P, E, runoff and soil moisture by season and for three different water resource regions. Focusing on the near future, 2021–2040, the new simulations project declines in surface-water availability across the southwest that translate into reduced soil moisture and runoff in California and Nevada, the Colorado River headwaters and Texas.
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This work was supported by NOAA awards NA08OAR4320912 and NA10OAR4310137 and NSF award AGS-08-04107. The comments of the wider Global Decadal Hydroclimate Variability and Change (GloDecH) group at Lamont are greatly appreciated.
The authors declare no competing financial interests.
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Seager, R., Ting, M., Li, C. et al. Projections of declining surface-water availability for the southwestern United States. Nature Clim Change 3, 482–486 (2013). https://doi.org/10.1038/nclimate1787
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